The invention relates to a service and parking brake assembly for vehicles. More particularly the invention is directed toward wheeled tractor type vehicles having a transmission driven by an engine, the transmission in turn driving the vehicle wheels, with the service and parking brake herein disclosed incorporated in the tranmission housing.
Although vehicle parking brakes have for a number of years utilized a braking element on the drive shaft of the vehicle, the vehicle service brakes are normally associated wit each driving wheel. Pneumatic, hydraulic and mechanical brake systems have been commonly used for service brake applications while the vehicle parking brake is normally of the mechanical type. In some cases the parking brake and the service brake and the service brakes have been consolidated, utilizing the same braking elements with different actuation means. Multiple disc brakes of the type utilized in heavy equipment generally require a cooling system to dissipate heat generated in the brake discs during actuation of the brakes. When such brakes are located in the wheel elements or in the vicinity of the wheel elements this cooling system requires extensive plumbing to communicate the cooling fluid to the brakes and return the cooling fluid to a heat exchanger for heat dissipation. Additionally, a fluid pump is needed to communicate the fluid to the various brake elements.
Placing the brake elements at the vehicle wheels requires a minimum of two brake assemblies although four brake assemblies are generally used on four wheeled vehicles with the possibility of additional brake assemblies in multi-wheeled vehicles.
It is apparent that to consolidate the braking requirements of a vehicle in a single brake assembly would be most desirable from the economic standpoint in that only a single brake assembly is necessary. Furthermore, the requirement for complex hydraulic systems or pneumatic systems to apply the brakes and to disengage the brakes may be considerably simplified. Additionally, the problem of providing cooling fluid to multiple disc brakes, mentioned above, may also be simplified. Further, to design a brake which is normally engaged, and is disengaged only while supplied with air pressure from the vehicle pneumatic system, provides the additional feature of a "fail-safe" system. That is, failure of the vehicle engine and the associated pneumatic system while the vehicle is underway automatically applies the brakes thereby bringing the vehicle to a stop and maintaining the vehicle in a stopped condition until the failed system can be repaired. These objects may be achieved by associating the service brakes and the parking brakes with the main drive shaft and utilizing the vehicle pneumatic system to disengage the braking elements associated with the aforesaid drive shaft.